103型机封(不包括轴套)的泄漏点有()个。
A.2
B.3
C.4
D.5
E.6
参考答案:C
Only a few hundred of these animals ______ today. [ ]
A. stay
B. remain
C. keep
D. left
切削时如已加工表面出现亮痕,则表示刀具与加工表面产生强烈的摩擦与挤压。